1. Technical Field of the Invention
The present invention relates to the field of infrared signalling or data transmission devices. In particular, the present invention is directed to an infrared signalling device of the type currently used on board naval vessels. The present invention is intended to reduce the weight, size and power requirements of existing infrared signalling and data transmission devices.
2. Description of the Background of the Invention
Conventional infrared signalling or beacon devices for use on board naval vessels generally utilize a powerful incandescent light source. A heavy red filter is positioned thereabout, which allows only the infrared frequencies of the light to be emitted by the filter. Such devices suffer from many drawbacks and disabilities, especially when used on board ships and especially when mounted at mast height on such ships. Incandescent infrared signalling devices are generally quite heavy. Their large weight results from their requirement of a visible light filter to filter out the visible light and allow only the infrared light to be transmitted. The weight of such incandescent devices is further increased by the need for an external cylindrical fresnel lens for focusing the infrared light emitted by the visible light filter. Further, the conventional infrared signalling devices must support the visible light filter and external fresnel lens, and thus require very heavy lamp supporting structures.
Further, the conventional infrared signalling and beacon devices lack any data transmission capabilities. Since the existing devices utilize incandescent lamps which generally employ tungsten filaments and which are heated to their glowing state, as their light source, these devices cannot be turned on and off at the high rates that would be required for data transmission. Thus the conventional infrared transmitters cannot perform digital data or voice transmission and communication at data rates greater than nine (9) words per minute.
A conventional prior art infrared signalling device currently used on board naval vessels is represented by the U.S. Navy's SAT 2N IR device. This infrared signalling and beacon device utilizes an incandescent bulb, a visible light filter and an external cylindrical fresnel lens to produce the beam of infrared light. The structure of this conventional device is quite massive, and use of a large incandescent bulb generates a substantial amount of heat energy which can damage the device.
The present invention discloses an infrared communication transmission system which utilizes semiconductor solid state devices instead of the incandescent bulbs and visible light filters of the prior art. Thus, a very substantial weight reduction compared to the conventional incandescent infrared transmitter is achieved by the elimination of the incandescent bulb, visible light filter, fresnel lens and the very heavy lamp supporting structure required by these components. The use of a solid state semiconductor device results in very efficient energy conversion, less generated heat to be dissipated, and a small size, of all which enable a much more compact and efficient design. In turn, the use of the more compact design results in enabling the further reduction of the size of the infrared transmitter and an even further reduction in the heat generated by the transmitter.
Further, the solid state communication transmitter of the invention has a data transmitting capability not available in existing infrared beacon and signalling devices. The use of solid state devices makes the present infrared communication transmitter very suitable for the modulation of the infrared energy that is required to achieve the high data rates necessary for digital data or analog voice communications.